JP2008111038A - Manufacturing method for pressure-sensitive adhesive sheet, and pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet attaining different pressure-sensitive adhesion characteristics on both surfaces by a single layer. <P>SOLUTION: When the pressure-sensitive adhesive sheet is manufactured, a predetermined substrate is coated with a solution prepared by mixing at least an inorganic filler of a flat shape and an organic substance dissolved in a solvent, the solution coated on the substrate is dried at an ordinary temperature for 2 minutes or more, and the solution is further dried at a higher temperature than the ordinary temperature at which the solvent is sufficiently dried to form the pressure-sensitive adhesive sheet having an inclination structure relative to a thickness direction. The solution is the one which uses 55% or more of the inorganic filler at a volume ratio of the whole of the solution and is adjusted to viscosity of 2,000 cps or less using the solvent for dissolving the organic substance. The substrate is coated with the solution such that a coated thickness after drying becomes 50 μm-180 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive sheet having adhesiveness on the surface and a method for producing a pressure-sensitive adhesive sheet.

  Conventionally, a functionally gradient material having a gradient structure in which constituent components and the like are changed continuously or stepwise with respect to the thickness direction has attracted attention in various fields. Even in a sheet product having a small thickness, a product having an inclined structure is known.

  Functionally graded materials that utilize the compatibility of polymer blends composed only of organic materials include phase-separated gradient structure blends, compatible gradient structure blends, and phase inversion gradient structure blends. The phase separation gradient structure blend is based on a solution casting method, in which a polymer blend solution is cast, and the gradient structure is adjusted using the phase separation formation process (self-assembly) at that time. The compatible gradient structure blend is based on a solution diffusion method. On the film made of the first polymer, a solution made of the second polymer is poured as a solvent for dissolving the first polymer, and the first polymer is made. The gradient structure is formed by controlling the rate of diffusion and dissolution of the film made of the second polymer into the solution made of the second polymer and the solvent evaporation rate. Further, the phase-inversion gradient structure blend is based on an injection molding method, and has an inclination structure in which the sea-island structure is inverted with respect to the thickness direction depending on the molding process conditions and the viscosity ratio of the constituent components.

  Further, by adding one or more inorganic fillers in the organic binder, and changing the amount and the presence ratio of the inorganic filler with respect to the thickness direction, an electrical or thermal property change is obtained. Functionally gradient materials have also been proposed (see, for example, Patent Document 1). Furthermore, it is known that mechanical properties such as adhesiveness can be changed by adopting an inclined structure in a polymer blend system.

Japanese Patent Laid-Open No. 8-73621

  Incidentally, in recent years, it has been proposed to use a magnetic sheet imparted with magnetic properties in the field of transponders and the like used in so-called RFID (Radio Frequency IDentification) systems. However, in the present situation, there is no magnetic sheet having an inclined structure in order to change the adhesiveness in the thickness direction.

  At present, as a technique for making the adhesive properties different between the front surface side and the back surface side of the magnetic sheet, simply attaching the adhesive sheet to either surface is performed. However, in the case where such a method cannot be taken, there is no choice but to impart adhesiveness to the binder itself constituting the magnetic sheet. Therefore, in the method of imparting tackiness to the binder, there is a problem that tackiness exists on both sides of the magnetic sheet, and a non-tacky film or the like needs to be affixed to the non-bonded side.

  In recent years, a mode in which a magnetic sheet using the magnetic properties of magnetic powder is attached to a flat cable or the like is also used. As a method of sticking to such a flat cable, it is common to use an adhesive, but in order to reduce the overall thickness and processing costs, the magnetic sheet itself may be sticky. desirable. At this time, it is a condition that the surface not adhered to the flat cable is not sticky. However, there is currently no single layer that realizes such different adhesive properties on both sides.

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of an adhesive sheet and an adhesive sheet which can implement | achieve the adhesive characteristic which is different in both surfaces by a single layer.

  The inventor of the present application, as a result of earnest research on the production of the pressure-sensitive adhesive sheet, is different on both sides by producing an inclined structure with respect to the thickness direction by controlling the density of the organic matter present around the inorganic filler. The inventors have found that the adhesive property can be realized by a single layer, and have completed the present invention.

  That is, the manufacturing method of the pressure-sensitive adhesive sheet according to the present invention that achieves the above-described object is a method for manufacturing a pressure-sensitive adhesive sheet having adhesiveness on the surface, and includes at least a flat inorganic filler and an organic substance dissolved in a solvent. A coating process in which a solution prepared under a predetermined material composition condition and a predetermined viscosity condition is applied on a predetermined base material under a predetermined coating condition, and the solution applied on the base material in the coating step A normal temperature drying step of drying at a normal temperature for a predetermined time or more, and the solution that has undergone the normal temperature drying step is dried at a temperature higher than the normal temperature at which the solvent is sufficiently dried, and has an inclined structure with respect to the thickness direction. And a high-temperature drying step for forming an adhesive sheet.

  In such a method for producing a pressure-sensitive adhesive sheet according to the present invention, when the solution is dried at room temperature, the amount of organic matter contained in the solution present around the flat inorganic filler is reduced. At this time, by drying at room temperature over a predetermined time, the organic matter settles from the surface side of the pressure-sensitive adhesive sheet toward the substrate side by its own weight. Accordingly, almost no organic component is present around the inorganic filler present on the surface side of the pressure-sensitive adhesive sheet, and the surface of the pressure-sensitive adhesive sheet has a shape in which only the inorganic fillers are non-uniformly arranged, resulting in a rough surface. Therefore, the pressure-sensitive adhesive sheet produced by the method for producing a pressure-sensitive adhesive sheet according to the present invention has almost no adhesiveness on the surface side of the pressure-sensitive adhesive sheet after drying, while the back surface side is on the base material side during normal temperature drying. The settled organic matter becomes a surface shape that reflects the smooth surface shape of the substrate, and has adhesiveness.

  In addition, the pressure-sensitive adhesive sheet according to the present invention that achieves the above-described object is a pressure-sensitive adhesive sheet having adhesiveness on the surface, and at least a flat inorganic filler and an organic substance dissolved in a solvent are mixed to obtain predetermined material composition conditions And a solution prepared under a predetermined viscosity condition as a main material, while making one surface sticky, while reducing the amount of the organic matter around the inorganic filler existing on the other surface side It is characterized by having an inclined structure with respect to the thickness direction so that the adhesiveness on the surface side is lowered.

  In such a pressure-sensitive adhesive sheet according to the present invention, there is almost no organic component around the inorganic filler present on the other surface side, and the surface has a shape in which only the inorganic filler is arranged non-uniformly, and has a rough surface. It becomes. Therefore, the pressure-sensitive adhesive sheet according to the present invention has almost no pressure-sensitive adhesiveness on the other surface side, but on one surface side, the organic material has a surface shape reflecting the smooth surface shape of the base material, and has a pressure-sensitive adhesive property. Will be.

  According to the present invention, it is possible to produce a single-layer pressure-sensitive adhesive sheet that has almost no adhesiveness on the front surface side and has adhesiveness only on the back surface side and has different adhesive properties on both sides.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  In this embodiment, the method for producing an adhesive sheet according to the present invention is applied to the production of a suitable magnetic sheet by sticking to a flat cable or the like. In particular, this magnetic sheet can achieve different adhesive properties on both sides in a single layer by controlling the density of the organic matter present around the inorganic filler and having an inclined structure with respect to the thickness direction. It can be done.

  First, before explaining the manufacturing method of a magnetic sheet, the structure of a magnetic sheet is demonstrated.

  The magnetic sheet is composed mainly of a magnetic paint composed of a solution in which at least a magnetic powder as an inorganic filler and an organic binder such as a polymer binder dissolved in a solvent are mixed.

  A flat soft magnetic powder is used as the magnetic powder. Arbitrary soft magnetic materials can be used as the magnetic material constituting the flat soft magnetic powder. For example, magnetic stainless steel (Fe—Cr—Al—Si based alloy), sendust (Fe—Si—Al based) Alloy), permalloy (Fe-Ni alloy), silicon copper (Fe-Cu-Si alloy), Fe-Si alloy, Fe-Si-B (-Cu-Nb) alloy, Fe-Ni-Cr- Si-based alloys, Fe-Si-Cr-based alloys, Fe-Si-Al-Ni-Cr-based alloys, and the like are suitable. A magnetic sheet manufactured using a soft magnetic powder made of these soft magnetic materials can be suitably used as a radio wave absorber because the soft magnetic powder is excellent in soft magnetic characteristics.

  Further, as the soft magnetic powder, a flat soft magnetic powder is used, but it is desirable to use a soft magnetic powder having a major axis of 1 to 200 μm and a flatness of 10 to 50. In order to equalize the size of the flat soft magnetic powder, classification may be performed using a sieve or the like as necessary.

  Furthermore, as the soft magnetic powder, for example, a soft magnetic powder that has been subjected to a coupling treatment using a coupling agent such as a silane coupling agent may be used. By using the soft magnetic powder subjected to the coupling treatment, the reinforcing effect between the flat soft magnetic powder and the polymer binder interface can be enhanced, and the specific gravity and corrosion resistance can be improved. As the coupling agent, for example, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane and the like can be used. The coupling treatment may be performed on the soft magnetic powder in advance, or may be performed at the same time when the soft magnetic powder and the binder are mixed, so that the coupling treatment is performed. Good.

  On the other hand, as the binder (polymer binder), a polyester resin, a polyurethane resin, an epoxy resin, or a copolymer thereof can be used. In particular, as the binder, it is possible to use a polyester-based resin which is a resin that has good processability and can orient a flat soft magnetic powder with high density. As the polyester resin used as the binder, a phosphorus-containing polyester resin having a phosphoric acid residue may be used. The magnetic sheet can be provided with flame retardancy by using this phosphorus-added polyester resin.

  As described above, the phosphorus-added polyester resin has a phosphoric acid residue in the molecule. Specific examples thereof include a phosphorus-modified saturated polyester copolymer. The phosphorus-modified saturated polyester copolymer is obtained by introducing a phosphorus component into the main skeleton of the saturated copolymer polyester, and is obtained by copolymerizing a polyester component and a phosphorus component. Here, as the polyester component, a polymer compound formed from ethylene glycol and terephthalic acid, naphthalenecarboxylic acid, adipic acid, sebacic acid or isophthalic acid, 1,4-butanediol and terephthalic acid, adipic acid or sebacic acid And a polymer compound formed from 1,6-hexanediol and adipic acid, sebacic acid, or isophthalic acid can be used. Moreover, as a phosphorus component, a phosphonate type polyol, a phosphate type polyol, a vinyl phosphonate, an allyl phosphonate, etc. can be used. Thus, the polyester copolymer in which the phosphorus component is introduced into the main skeleton exhibits flame retardancy higher than that obtained by simply mixing and dispersing the phosphorus component in the polyester.

  The phosphorus content of the polyester resin containing phosphorus depends on the type of the main skeleton of the polyester resin, the type of phosphorus component (phosphoric acid residue), and the type of other components constituting the magnetic sheet. However, the phosphorus content is 0.5 wt% to 4.0 wt%. When the phosphorus content is less than 0.5% by weight, flame retardancy is low, and sufficient flame retardancy cannot be obtained unless a large amount of flame retardant is added. On the other hand, if it exceeds 4.0% by weight, the molecular weight of the polyester resin cannot be increased, so that the mechanical strength is lowered.

  Further, the number average molecular weight of the phosphorus-containing polyester-based resin is desirably 8000 to 50000. If the number average molecular weight is less than 8000, the resulting magnetic sheet may have insufficient mechanical strength. On the other hand, when the number average molecular weight is larger than 50000, the obtained magnetic sheet becomes hard, and thus desired flexibility cannot be obtained. The glass transition temperature of the phosphorus-added polyester resin is desirably -20 ° C to 40 ° C. When the glass transition temperature is −20 ° C. or lower, the elastic modulus is lowered at a high temperature, and the adhesive force between soft magnetic powders is lowered in a high temperature environment or a high temperature and high humidity environment. On the other hand, when the glass transition temperature exceeds 40 ° C., the magnetic sheet becomes hard at room temperature.

  Furthermore, you may make it add the dispersion | distribution particle | grains disperse | distributed to a polyester resin, without being compatible with the polyester resin which is a binder to a magnetic coating material. Due to the dispersed particles, the magnetic sheet has a smooth surface and can have a good appearance such that no traces of air in the polyester resin remain when compressed in a subsequent step. Here, the dispersed particles are preferably insulative. Furthermore, if the dispersed particles are a flame retardant, flame retardancy can be imparted to the magnetic sheet.

  Any flame retardant can be used, and examples thereof include a zinc-based flame retardant, a nitrogen-based flame retardant, and a hydroxide-based flame retardant. Furthermore, magnesium hydroxide, aluminum hydroxide, etc. can be mentioned. Examples of the zinc-based flame retardant include zinc carbonate, zinc oxide, and zinc borate. Among these, zinc carbonate is preferable. As the nitrogen-based flame retardant, for example, melamine derivatives such as melamine (cyanuric acid triamide), ammelin (cyanuric acid diamide), ammelide (cyanuric acid monoamide), melam, melamine cyanurate, benzoguanamine and the like can be used. In addition, it is desirable to use melamine cyanurate from the viewpoints of dispersibility in polyester resins and mixing properties. Further, carbon black, titanium oxide, boron nitride aluminum nitride, alumina or the like may be added instead of the flame retardant.

  The weight of the dispersed particles is preferably 7/13 or less with respect to the weight of the polyester resin. If the weight of the dispersed particles that are dispersed incompatible with the polyester-based resin is 7/13 or less with respect to the weight of the polyester-based resin, the high-temperature environment or high-humidity remains with good magnetic properties. The dimensional change that the thickness of the magnetic sheet changes under the environment can be suppressed, and good workability can be obtained. On the other hand, when the weight of dispersed particles is added to the polyester resin more than 7/13, the dimensional change of the thickness of the magnetic sheet in a high temperature environment or a high temperature and high humidity environment can be suppressed. It will fall.

  Moreover, it is preferable that the particle size of the dispersed particles dispersed without being compatible with the polyester resin is 0.01 μm to 15 μm. If the particle diameter of the dispersed particles is less than 0.01 μm, the effect of suppressing the change in the thickness of the magnetic sheet cannot be obtained. Moreover, if the particle diameter of the dispersed particles is 15 μm or more, the magnetic properties will be deteriorated.

  When a magnetic sheet is compressed and manufactured, the air in the resin is discharged to increase its specific gravity. However, the air passage is usually limited by the compression. Moreover, the soft magnetic powder blended in a large amount overlaps, so that the binder does not reach a very thin gap, and inevitably voids remain. On the other hand, since the magnetic sheet to which the dispersed particles are added is formed smoothly, the amount of air contained in the magnetic sheet can be reduced and the specific gravity can be increased. That is, the magnetic sheet can obtain good magnetic properties. In addition, in the magnetic sheet, when the specific gravity is increased by compression, the amount of air contained in the inside is reduced, so that the flame retardancy can be further improved.

  Moreover, the magnetic sheet may contain a crosslinking agent in addition to the soft magnetic powder and the polyester resin as the binder. Examples of the crosslinking agent include blocked isocyanate. The blocked isocyanate is an isocyanate compound protected with a protecting group that can be dissociated (deprotected) by heating so that the isocyanate group (—NCO) does not react at room temperature. This blocked isocyanate does not crosslink the polyester resin at room temperature, but when heated above the dissociation temperature of the protecting group, the protecting group is dissociated, the isocyanate group is activated, and the polyester resin is crosslinked.

  In addition, as block isocyanate, it is desirable to use the thing whose dissociation temperature of a protective group is 120 to 160 degreeC. By making this dissociation temperature higher than 120 degreeC, the methyl ethyl ketone and toluene used in order to adjust the viscosity of the magnetic coating material apply | coated on a base material can be evaporated, and the magnetic sheet formed can be dried. On the other hand, when the dissociation temperature is lower than 120 ° C, the protective group of the blocked isocyanate is dissociated when the magnetic paint is applied onto the substrate and dried at a temperature higher than the boiling point of methyl ethyl ketone or toluene. Therefore, there is a possibility that the crosslinking of the polyester resin proceeds. Moreover, since the heat-resistant temperature of the film used for the substrate is 160 ° C. or lower, the dissociation temperature is desirably 160 ° C. or lower. The reaction for crosslinking the polyester resin proceeds slowly even at room temperature, so after the heating is completed, the whole is cooled to room temperature and left for a long time, so that the polyester resin is completely crosslinked and the binder is completely cured. Become.

  Moreover, it is desirable that the blocked isocyanate is blended in an amount of 0.5% by weight or more based on the polyester resin as a binder. Thereby, a sufficient effect can be obtained. When the blended amount of the blocked isocyanate is less than 0.5% by weight, the crosslinking becomes insufficient, and the change in thickness may be increased in a high temperature environment or a high humidity environment.

  Furthermore, when an unprotected isocyanate is used, when the magnetic coating is applied onto the substrate and the solvent is dried to form a sheet, crosslinking of the polyester resin proceeds. However, good magnetic properties cannot be obtained. Moreover, since the hardened thing is compressed, the change that thickness becomes thick becomes large.

  Here, it is not easy to mix flat soft magnetic powder with a polyester-based resin as a binder and fill it with high density. When the flat soft magnetic powder is mixed with the binder, the flat soft magnetic powder may be crushed and reduced by the load during mixing, or the permeability μ ′ may be reduced due to a large strain. Because it becomes. For this reason, a polymer binder dissolved in a solvent is used to mix the flat soft magnetic powder and the binder, and the flat soft magnetic powder is mixed as much as possible so that no load is applied. It is desirable to produce a magnetic sheet by coating the base material on the substrate.

  When applying the magnetic paint, by applying a magnetic field, the effect of aligning and arranging the flat soft magnetic powder in the in-plane direction can be obtained, and the soft magnetic powder can be filled with high density. Moreover, in order to improve specific gravity, you may compress the dried magnetic sheet. By increasing the specific gravity of the magnetic sheet, the amount of air contained therein is reduced, so that the flame retardancy can be further improved.

  Moreover, as a base material, a film-form thing can be used, for example, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyimide film, a polyphenylene sulfide film, a polypropylene film, a polyethylene film, a polypropylene film, a polyamide film etc. are mentioned. be able to. Moreover, the thickness can be selected suitably, for example, can be several micrometers-several hundred micrometers. Furthermore, it is desirable that a release agent is applied to the magnetic sheet forming surface.

  Further, in order to facilitate orientation, it is desirable that the resin as the binder has a high fluidity, and it is desirable to dissolve the binder in a solvent to obtain a magnetic paint having a predetermined viscosity. Various solvents can be used to adjust the viscosity of the magnetic coating material. For example, aromatic hydrocarbon compounds such as benzene, toluene, and xylene, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, and the like can be used. In order to adjust the application shape of the magnetic paint, a high boiling point solvent such as diacetone alcohol may be added in a small amount of 5% or less.

  The viscosity of the magnetic paint may be adjusted so that it can be applied using a coater, doctor blade method, etc. However, if the viscosity is too low, the binder component will increase, so the specific gravity will decrease when it is made into a sheet. There is a problem of end. The solid content is desirably in the range of 50% to 70%. If the solid content is 70% or more and the viscosity is large, there is a possibility that inconveniences such as inability to apply or streaking in the sheet during application may occur. When the solid content is 50% or less, problems such as repelling with the release agent on the base material occur when the magnetic paint is applied on the base material.

  The magnetic sheet shown as an embodiment of the present invention is manufactured using a magnetic paint having such a structure as a main material. Below, the manufacturing method which provides adhesiveness to the surface of this magnetic sheet is demonstrated.

  In the magnetic sheet, when the organic substance such as the organic binder described above and the magnetic powder that is the inorganic filler are present uniformly, if an organic substance having adhesiveness at room temperature is used, both surfaces of the magnetic sheet are used. It will be sticky. In the method for producing a magnetic sheet shown as an embodiment of the present invention, the material composition, viscosity, coating conditions and drying conditions of the magnetic paint are controlled, and the gradient structure due to the density of organic matter present around the inorganic filler is in the thickness direction. Thus, when the base material side is the back surface, the back surface side is made sticky while the surface side stickiness is lowered.

  First, in manufacturing a magnetic sheet, the material composition condition is that flat magnetic powder is used in a volume ratio of 55% or more of the entire magnetic coating material. Moreover, when manufacturing a magnetic sheet, it is made into viscosity conditions to adjust the viscosity of a magnetic coating material to 2000 cps or less using the solvent in which an organic binder melt | dissolves.

  When manufacturing a magnetic sheet, the gap is adjusted so that the coating thickness after drying of the magnetic coating material prepared according to such material composition and viscosity is 50 μm to 180 μm using a coating machine such as a pipe coater. Then, it is applied onto a predetermined substrate. This is the application condition of the magnetic paint.

  And in manufacturing a magnetic sheet, after drying the magnetic coating material apply | coated on the predetermined | prescribed base material according to such application | coating conditions for 2 minutes or more using normal temperature air of about 20 to 40 degreeC, The magnetic sheet is formed by drying at a high temperature of about 80 ° C. to 115 ° C. so that the solvent is sufficiently dried. This is the drying condition of the magnetic paint. The reason why the room temperature drying step is provided first is to prevent unnecessary evaporation of the solvent. The upper limit of the temperature in the high-temperature drying step is 115 ° C., but this temperature is taken into consideration when a crosslinking agent is contained, and should be lower than the crosslinking start temperature of the crosslinking agent. . Furthermore, it is desirable to perform the high temperature drying to such an extent that the solvent content is 1% or less. When the content of the solvent is 1% or more, when the dried magnetic sheet is peeled off from the substrate, it may be stretched or torn, and the evaporated solvent swells on the surface of the magnetic sheet. Because it appears.

  The magnetic sheet is manufactured according to such a manufacturing method. Here, at the stage where the magnetic paint is applied on the base material in a series of manufacturing processes, the flat magnetic powder or solvent is in a slurry state so that it cannot move freely in the solution, but the room temperature drying process At this time, the amount of the binder contained in the solution present around the flat magnetic powder is reduced. At this time, since the drying speed is slow, that is, the room temperature drying is performed for a long time of 2 minutes or more, the binder settles from the surface side of the magnetic sheet toward the substrate side by its own weight. Accordingly, almost no binder component is present around the magnetic powder present on the surface side of the magnetic sheet, and the surface of the magnetic sheet has a shape in which only the magnetic powder is non-uniformly arranged, resulting in a rough surface. Due to this rough surface, the dried magnetic sheet has almost no adhesiveness on the surface side, and can be wound without using a peeling substrate or the like. On the other hand, on the back side of the magnetic sheet, the binder that settled on the substrate side during the room temperature drying step becomes a surface shape that reflects the smooth surface shape of the substrate, depending on the state of the substrate surface smoothness, etc. It has the adhesiveness determined in this way. In addition, when performing a series of normal temperature drying process and high temperature drying process by a line, drying time will be adjusted by adjusting the line speed which conveys the magnetic coating material apply | coated on the base material. In this case, in the course of the drying process, not only the binder but also the magnetic powder settles, but in producing the magnetic sheet, the line speed depends on the viscosity of the magnetic paint and the time that the magnetic powder settles in the magnetic paint. You can decide.

The magnetic sheet may be manufactured using a spherical magnetic powder instead of a flat magnetic powder. However, when the spherical magnetic powder is used, the above-mentioned surface-side adhesiveness is reduced. This phenomenon is unlikely to occur. Specifically, since the surface of the spherical magnetic powder has a uniform shape and no irregularities, the binder is likely to cover the surface. Therefore, for example, as shown in FIG. 1, when a magnetic coating material produced using such a spherical magnetic powder _MSH is applied onto a predetermined base material B and dried, the particle size of the magnetic powder _MSH is as follows. If it is about 35 μm or less, the substantially uniformly dispersed magnetic powder _MSH will remain in a substantially uniformly dispersed state after drying, and as a result, the surface of the magnetic sheet will be substantially flat and the magnetic powder It would exhibit tack by the binder adhering to the surface of the M _SH. On the other hand, flat magnetic powder usually has fine cracks and irregularities on its surface, and even if it is `` flat shape '', it is warped in any direction as well as planar shape There are many. Therefore, for example, as shown in FIG. 2, when a magnetic coating material produced using such a flat magnetic powder M _NSH is applied onto a predetermined substrate B and dried, the ends of the magnetic powder M _NSH are It tends to protrude from the surface of the magnetic sheet. In other words, it is difficult for the surface of the magnetic sheet using the flat magnetic powder M _NSH to make the binder uniformly present, and as a result, it is difficult for the binder to contact the surface of the magnetic powder M _NSH. As a result, the tackiness is lowered.

  As described above, the method for producing a magnetic sheet shown as an embodiment of the present invention controls the material composition, viscosity, coating conditions, and drying conditions of a magnetic coating material, and the density of organic substances present around inorganic fillers is controlled. By providing the inclined structure with respect to the thickness direction, it is possible to manufacture a single-layer magnetic sheet having adhesiveness on the back surface side and reduced adhesiveness on the front surface side. Also, when storing the magnetic sheet produced by this production method, there is no problem even if a peeling film is not attached to the surface side because it is not sticky on the surface side, and it is necessary to use such a film. Therefore, the process of peeling the film in the next process can be eliminated. Furthermore, in order to control the magnetic properties, there are cases where magnetic sheets are overlapped and used, but since there is no adhesive on the surface side, the alignment work at the time of overlapping is simplified and the yield can be improved. it can.

[Example]
The inventor of the present application actually manufactured a magnetic sheet, and measured the presence or absence of adhesiveness on the front surface and the back surface, and the magnetic properties (permeability μ ′).

  Specifically, as shown in the following Table 1, four types of magnetic paints A to D having different material compositions and viscosities were prepared. The magnetic coating A is a spherical magnetic powder having a particle size distribution D of 50 and an average particle size of 35 μm Fe-Si-Al alloy powder (manufactured by Mate Co., Ltd.) 500 parts by weight, a binder having a glass transition temperature Tg of 100% by weight of a polyester resin (UE3230; manufactured by Unitika Ltd.) at −20 ° C., a mixed solvent of toluene and methyl ethyl ketone (MEK) as a solvent, and a magnetic powder and a binder as a solid content of 63% It adjusted and produced so that it might become. In addition, the magnetic coating B is made of a Fe-Si-Al alloy powder having a flat shape with a binder and solvent of the same material and the same composition as the magnetic coating A, and having a particle size distribution D of 50 and an average particle size of 45 μm. It was produced using 500 parts by weight instead of Mate Co., Ltd. Furthermore, the magnetic coating material C was produced by using the same material as the magnetic coating material B and reducing the magnetic powder to 300 parts by weight. Furthermore, the magnetic coating material D was prepared by replacing the polyester resin (Byron # 200; manufactured by Toyobo Co., Ltd.) having the same composition as the magnetic coating material B and having a glass transition temperature Tg of 67 ° C. All of these magnetic paints A to D were prepared by enclosing a material in a predetermined container and rotating the container using a stirrer. The composition of the mixed solvent of toluene and methyl ethyl ketone is preferably toluene / methyl ethyl ketone = 5 / 5-9 / 1. This is because when the composition ratio of methyl ethyl ketone is larger than this range, the surface shape of the magnetic sheet is deteriorated due to the influence of moisture in the air when the magnetic paint is applied.

In Comparative Example 1, magnetic paint A is used, in Comparative Example 2, Examples 1 and 2, magnetic paint B is used, in Comparative Example 3, magnetic paint C is used, and in Comparative Example 4, magnetic paint D is used. Using. In any of Examples 1 and 2 and Comparative Examples 1 to 4, the gap of the roll coater was set to 500 μm, each magnetic paint was applied on a peeling PET (polyethylene terephthalate) film as a substrate, and dried at room temperature. A temperature gradient of 20 ° C. was applied as a process, and a temperature gradient of 80 ° C. and 115 ° C. was applied as a high-temperature drying process. At this time, the drying speed was changed by changing the line speed, and the presence / absence of adhesiveness on the front and back surfaces of the magnetic sheet after drying and the magnetic characteristics (permeability μ ′) were measured. The presence / absence of adhesiveness was measured using a tack tester. As a result, a material having a load of 5 g / cm ² or more was determined to be “adhesive”. Magnetic properties were measured by using an impedance analyzer to measure the magnetic permeability μ ′ of a sample obtained by processing a magnetic sheet into a toroidal ring shape of φ7 mm. The results are shown in Table 2 below.

(Example 1)
The magnetic coating B applied on the peeling PET was dried with the line speed set at 1.5 m / min to obtain a magnetic sheet. As a result, since the room temperature drying process takes 2 minutes or more, it passes between the flat magnetic powders and the binder settles on the base material side to exhibit an inclined structure, and the surface side becomes a rough surface and becomes sticky. The adhesiveness was lost, and the back side showed adhesiveness due to the settled binder. Further, the magnetic properties were as high as the magnetic permeability μ ′ was as high as “25”.

(Example 2)
The magnetic coating B applied on the peeling PET was dried at a line speed of 1 m / min to obtain a magnetic sheet. That is, in Example 2, the drying time is longer than that in Example 1. As a result, as in Example 1, while the surface side became rough, the tackiness disappeared, while the back side showed tackiness due to the settled binder, and the magnetic properties were also good values. .

(Comparative Example 1)
The magnetic coating A applied on the peeling PET was dried with the line speed set at 1.5 m / min to obtain a magnetic sheet. That is, in Comparative Example 1, a magnetic coating material produced using a spherical magnetic powder was dried for the same drying time as in Example 1. As a result, although the binder is distributed slightly more on the substrate side than on the front side, it does not exhibit a sufficient inclined structure as in Examples 1 and 2, and the adhesiveness is not different between the front and back sides. It was. Further, the magnetic properties were such that the magnetic permeability μ ′ was as low as “10”.

(Comparative Example 2)
The magnetic coating B applied on the peeling PET was dried at a line speed of 3 m / min to obtain a magnetic sheet. That is, Comparative Example 2 is obtained by drying a magnetic coating material produced using a flat magnetic powder in a short room temperature drying process of about 1 minute. As a result, because the time of the room temperature drying process is short, sufficient time for the binder to move to the base material side cannot be taken, and due to this, no inclined structure is exhibited, and no change in the adhesiveness on the surface side could be confirmed. .

(Comparative Example 3)
The magnetic paint C applied on the peeling PET was dried at a line speed of 1.5 m / min to obtain a magnetic sheet. That is, in Comparative Example 3, the magnetic coating material produced by reducing the weight part of the flat magnetic powder was dried for the same drying time as in Example 1. As a result, although the binder volume is larger than the magnetic powder, the binder is settled on the substrate side, but the phenomenon of roughening the surface does not occur physically and exhibits an inclined structure. Therefore, no change in the adhesiveness on the surface side could be confirmed.

(Comparative Example 4)
The magnetic coating material D applied on the peeling PET was dried at a line speed of 1.5 m / min to obtain a magnetic sheet. That is, in Comparative Example 4, a magnetic coating material produced using a binder having a high glass transition temperature was dried for the same drying time as in Example 1. As a result, the glass transition temperature of the binder is higher than the temperature in the room temperature drying process, and the binder is in a frozen state at this temperature, so the binder is not sticky. For this reason, even if an inclined structure was exhibited, no tackiness was observed on the front and back surfaces.

  From these results, it can be seen that the manufacturing method proposed in the present invention is extremely effective. In Examples 1 and 2 and Comparative Examples 1 to 4, Fe-Si-Al alloy powder was used as the magnetic powder, and a polyester resin was used as the binder. It is easily guessed that similar results can be obtained even in combination.

  In the above-described embodiment, the magnetic sheet is used as a specific example of the pressure-sensitive adhesive sheet. However, the present invention mixes at least a flat inorganic filler such as a metal paint and an organic substance dissolved in a solvent. Any solution can be used as long as it has a prepared solution as a main material and has adhesiveness. Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

It is a figure for demonstrating the mode at the time of apply | coating the magnetic coating material produced using spherical magnetic powder on a predetermined base material, and making it dry. It is a figure for demonstrating a mode at the time of apply | coating the magnetic coating material produced using the flat-shaped magnetic powder on a predetermined base material, and making it dry.

Explanation of symbols

B base material M _SH , M _NSH magnetic powder

Claims (14)

A method for producing an adhesive sheet having adhesiveness on the surface,
An application step of applying a solution prepared by mixing at least a flat inorganic filler and an organic substance dissolved in a solvent under a predetermined material composition condition and a predetermined viscosity condition onto a predetermined substrate under a predetermined application condition; ,
A room temperature drying step of drying the solution coated on the substrate in the coating step at room temperature for a predetermined time or more;
The solution that has undergone the room temperature drying step is dried at a temperature higher than the room temperature so that the solvent is sufficiently dried, and a high temperature drying step is performed to form an adhesive sheet having a tilted structure with respect to the thickness direction. A method for producing a pressure-sensitive adhesive sheet. The material composition condition is to use 55% or more of the inorganic filler in a volume ratio of the whole solution,
The viscosity condition is to adjust the viscosity of the solution to 2000 cps or less using the solvent in which the organic matter is dissolved,
The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the application condition is that the solution is applied on the base material so that a coating thickness after drying is 50 μm to 180 μm. In the said normal temperature drying process, the said solution is dried for 2 minutes or more. The manufacturing method of the adhesive sheet of Claim 1 characterized by the above-mentioned. In the said normal temperature drying process, the said solution is dried using normal temperature air of 20 to 40 degreeC. The manufacturing method of the adhesive sheet of Claim 3 characterized by the above-mentioned. The method for producing a pressure-sensitive adhesive sheet according to claim 1 or 4, wherein, in the high-temperature drying step, the solution is dried at a temperature of 80C to 115C. In the room temperature drying step and the high temperature drying step, the solution applied on the substrate is conveyed at a line speed determined according to the viscosity of the solution and the time during which the inorganic filler settles in the solution. The manufacturing method of the adhesive sheet of Claim 1 characterized by these. The above solution contains a crosslinking agent,
The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the drying temperature in the high-temperature drying step is lower than the crosslinking start temperature of the crosslinking agent. The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the high-temperature drying step is performed such that the content of the solvent is 1% or less. The solution is a magnetic coating prepared by mixing a flat magnetic powder as the inorganic filler and a binder as the organic substance dissolved in the solvent,
The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet is a magnetic sheet produced using the magnetic paint as a main material. An adhesive sheet having adhesiveness on the surface,
A solution prepared by mixing at least a flat inorganic filler and an organic substance dissolved in a solvent under a predetermined material composition condition and a predetermined viscosity condition as a main material,
While making one surface sticky, while reducing the organic matter around the inorganic filler present on the other surface side to reduce the adhesiveness on the other surface side, An adhesive sheet characterized by having an inclined structure. The solution applied on a predetermined substrate while controlling the application conditions of the solution is dried at room temperature for a predetermined time or more, and further dried at a temperature higher than the room temperature so that the solvent is sufficiently dried. The pressure-sensitive adhesive sheet according to claim 10, wherein the pressure-sensitive adhesive sheet is formed so as to have the inclined structure. The material composition condition is to use 55% or more of the inorganic filler in a volume ratio of the whole solution,
The viscosity condition is to adjust the viscosity of the solution to 2000 cps or less using the solvent in which the organic matter is dissolved,
The pressure-sensitive adhesive sheet according to claim 11, wherein the application condition is that the solution is applied on the base material so that a coating thickness after drying is 50 μm to 180 μm. The pressure-sensitive adhesive sheet according to claim 11, wherein the solution is dried for 2 minutes or more in the room temperature drying step. The solution is a magnetic coating prepared by mixing a flat magnetic powder as the inorganic filler and a binder as the organic substance dissolved in the solvent,
The pressure-sensitive adhesive sheet according to claim 10, wherein the pressure-sensitive adhesive sheet is a magnetic sheet manufactured using the magnetic paint as a main material.